An Amperometric Immunosensor for the Newcastle Disease Antibody Assay

An amperometric immunosensor system for assay of an important poultry infectious disease Newcastle disease antibody (ND.Ab) has been developed. The Newcastle disease antigen (ND.Ag) was immobil- ized in a graphite paste matrix. The assay procedure is based on the bioreaction of the analyte ND.Ab and enzyme labeled HRP-ND.Ab competing for the ND.Ag sites at the newly regenerated biocomposite surface. The determination is accomplished by amperometry using tetramethylbenzidine and H2O2 as the substrates. Two different graphite pastes were compared using either sol–gel or solid paraffin as binders. The sol–gel biocomposite showed a better response characteristics and higher reproducibility. The ND.Ab can be determined up to 443.24 ng/mL with a detection limit of 11.1 ng/mL. The recovery studies in serum samples show the feasibility of practical application of the proposed method.